Field of the Invention
The present invention relates to a driving device, a control method therefor, and an image pickup apparatus, and in particular, relates to the driving device provided in an image stabilizer of an image pickup apparatus, such as a digital camera.
Description of the Related Art
An image pickup apparatus is provided with an image stabilizer for correcting a blur of an image formed on an image pickup surface through an optical system. The image stabilizer controls to move an optical element in the optical system in response to a shake due to an external force in order to reduce a blur of an image. Then, the image stabilizer is needed to move the optical element largely in order to correct a large shake.
For example, there is an image stabilizer that uses a voice coil motor (VCM) as a driving source and that reduces decline in a driving efficiency without enlarging the driving device when the optical element is largely moved (see Japanese Laid-Open Patent Publication (Kokai) No. 2000-19577 (JP 2000-19577A)).
The image stabilizer disclosed in the above-mentioned publication arranges the VCM so that a center of a voice coil is coincident with a center of a magnet when viewed in an optical axis direction. Then, a moving part on which the optical member is mounted is moved by moving the voice coil around the center of the magnet as a drive center. In this case, when viewed in the optical axis direction, a thrust in a moving direction becomes zero when the center of the voice coil is located near a position where magnetic flux density of the magnet is maximized. Accordingly, it is necessary to enlarge the width of the magnet and the width of the coil in order to increase the movable amount of the moving part.
However, when the width of the magnet and the width of the coil increase, the diameter of the driving device increases more than the addition of the movable amount. That is, when the image stabilizer using the VCM as a driving source expands the movable amount, the diameter of the driving device increases more than the addition of the movable amount.